Piston



R. E. DAY

July 14, 1936.

PISTON m 7 A I A I RAY EBAY M W q'gw/ ATTORNEY.

Original Filed July 18, 1932 Patented July 14, 1936 Ray E. Day, Detroit, Mich.

Application July 18, 1932, Serial No. 623,064 Renewed April 18, 1936 3 Claims. (01. 309-11) This invention relates to pistons for internal combustion engines, and particularly to pistons made from aluminumalloy, which on account of the relatively high co-.-eflicient of expansion 5 of the metal, expand to such a degree under opcrating conditions as to require either an undesirable initial clearance within the cylinders, or the provision of means to control the expansion so that a substantially uniform clearance may be maintained during operation.

I have found that there are two principal factors which control the successful manufacture and sale of a low price commercially practical pis ton., First, the design of the piston must be simplified in order to facilitate casting of the pistons and t6 reduce the cost of manufacture. Second,

the piston must be so constructed in simplified manner as to take care of expansion and contraction under operating conditions, maintain a nearly uniform operating fit in the cylinder, and effectually guide the piston in order to prevent rocking or tilting of the piston and piston slap.

An object of the present invention is to provide a piston of simplified construction which can be produced cheaply and which at the same I time is constructed in improved manner'so as to have the desired high degree of emciency in operation without resorting to structural expedients, many of questionable value, as heretofore. Other objects of this invention will appear in the following description and appended claims, reference being had to'the'accompanying drawing forming a part of this specification wherein like reference characters designate correspondingparts in the several views.

Figslis a side elevation of a piston embodying my invention.

Fig. 2 is a vertical section taken substantially alongthe line 2-2 of Fig. 1, looking in the direc- 40 tion'of the arrows.

Fig. 3 is an'elevation of the opposite side of the piston shown in Fig. 1. a

Fig. 4 is a horizontal section taken substanr tion it is to be understood that the invention is 50 not limited in its application to the details. of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in. various ways. Also it 155 is to be understood that the phraseology or terminology employed herein is for thepru-pose'of description and not ,of limitation, and it is not intended to limit the invention claimed herein beyond'the requirements of the prior art.

60 Referring now particularly to the drawing, I

a piston. i

The side of the skirt H, at a point between the piston pin bosses, is traversed by a substantially 5 have shown an aluminum alloy piston having a head 9 provided with piston ring grooves l0 separated by lands Ilia, a skirt ll, piston pin bosses I2 and 13 provided with piston pin openings II ---and I5, respectively. The piston head 9 is pro- 5 vided with a transverse reenforcing web l6 which has depending. portions lBa formed integrally with the piston pin bosses l2 and I3. The skirt portion of the piston is provided with an internal circumferential reenforcing rib l1 preferably'located immediately below the horizontal slit i8.

which serves to'separate a portion of the head 9 from the skirt ll. The skirt II is provided at one side with a relieved area shown as a whole at l9, which sur- 15 rounds the piston pin opening it and extends to the top of the skirt on one side of and above the opening, as shown at I9a. On the opposite side of the piston pin opening I 4, the relieved area l9 terminates at a point adjacent the top of the skirt to provide a bearing strip or portion 2| which preferably tapers ofi slightly, as shown at Zia, toward ,the open relieved area. Within the relieved area the skirt is provided with a curved slot having a substantially arcuate por- 25 tion 23 and a horizontally extending portion 23a. The portion 23 of the slot terminates at a point adjacent and slightly below the taper 2km The horizontal portion 23a of the slot extends along the lower edge of the relieved area l9 adjacent the 30 curved bearing portion at the bottom of the skirt.

, The relieved area I9 is unbalanced or divided into area 20 surrounding the piston pin opening l5 and extending to the top of the skirt at one side of the opening, as shown at 20a; On the other side of the opening, this relieved area terminates at a point below the top of the skirt or the horizontal slot l8 to provide a bearing strip or portion 22 tapered oif'at 22a. The skirt within the relieved area 20 is likewiseprovided with a curved slot having an arcuate shaped portion 24 and a horizontal portion 24a. It will be seen that the relieved areas I9 and 20 and their associated parts are identical on both sides of the vertical slit 25, which, in actual practice, preferably extends from the bottom edge of the skirt to the horizontal slit l8. The lower ,port'ion of the skirt is provided with an internal circumferential reenforcing rib 2 6, to the rib ll, so

which extends part way around the pistonbetween the-head and skirt. The skirt H is provided at each side with a relieved area 28 surrounding'thepiston pin opening l5 and extending to the upper edge of the skirt at a point immediately above the opening IS. The area 28 however, adjacent its side edges is terminated at points adjacent the upper edge of the skirt to provide a pair of opposedhorizontal bearing strips or portions 26a and 28b. The relieved area 28 is provided preferably with a substantially U-shaped curved slot 29 which conforms to the shape of the piston pinopening l5, and extends around the bottom and sides thereof, the lower portion of the curved slot extending preferably to the extreme lower edge of the relieved area 28 adjacent the lower bearing surface of the skirt. The other structural features of the piston of Fig. 5 are identical. with those ofthe preceding figures. It will be noted that the relieved area 28 x is unbalancedand is wider on the split side of the piston as shown at 0, than on the opposite or high thrust side of the piston, as shown at d.

From the foregoing it will be noted that the head and skirt are separated from each other on one side of the piston pin bosses by the horizontai slit I8. On this same side the skirt is longitudinally split by the substantially vertical slot 25, so that one side of the piston is freely compressible. The piston pin bosses are partially separated from the skirt by the slots 23, 23a;

- be drawn out of round and excessive wall pres-Y sure would be set up in the'direction of the wrist :24; 24a; and 29, which permit the bosses to expand or move outwardly with the head without transmitting this expansion to the annular bearing portion below the bosses or to the split side f.the skirt. The separation of the major part of the bosses from the skirt gives an appreciable amount of freedom between the bosses and the skirt and'permits the entire lower portion of the skirt to remain substantially round at all times. The ribs or annular trusses l1 and 26 assist materially in maintaining the skirt portion round while permitting expansion and contrac-.

tion thereof. If the skirt were notseparated from the bosses by these curved slots, it would pin-bosses. In practice, the piston is placedin the engine cylinder in" such a position that the reaction due to the compression will be directed against the relatively resilient or'split side of the piston, while the reaction due to the explosion,-

which is much greater, will be directed against the side where the head and skirt are integral or continuous. r

It will be seen that the widest portion of each unbalanced relieved area is on the compression or split side ,of the piston, whereas the smaller portion ofthe relieved area is on the explosion or high thrust side. Since the high thrust side of the piston is subjected to greater pressure than the low thrust side I have found it preferable to have a larger bearing surface on the high into the relieved area between the curved 'slot and located above and adiacent thrust side. By thus reducing the area-of the bearing surface onthe low thrust or compression side of the piston-it. will be seen that the flexibility of that side of the piston is increased to eliminate any possibility of binding of the piston.

With previous types of pistons having resilient skirt portions provided with open relieved areas. it has been found that there was a tendency of the piston to rock or tilt in the cylinder, causing the objectionable slapping of the piston. This is obviated in the construction shown in Figs. 1 to 4 by thebearing strips or portions 2| and 22, lo-

- cated above the relief on the resilient side of the piston. These bearing strips or surfaces also help to guide the piston during its reciprocation within the cylinder. In the form shown in Fig. 5, two horizontally disposed bearing strips or portions 28a and 28b are provided, which, together with the bearing portion of the skirt below the relief 28, serve to guide the piston in the cylinder and ;also to prevent it from rocking. These bearing portions thus assist in guiding the piston at points between the skirt and the lower ring groove, but they are' interrupted or relieved in the integral relieved areas through which the bosses are united to .the head so as not to interfere with the outward movement ofthe bosses.

, slot located wholly within the relieved area spaced from and extendingpartly around each opening p to partially separate the piston pin boss from the skirt, and a narrow bearing portion extending said circumferential slit.

2. In a piston, the combination of a head, a

' skirt, and piston pin bosses, the head and skirt 3. In a piston; the combination of a head Maw 'ing grooves therein, a skirt and piston pin bosses, the head and skirt being continuous atone side of the bosses and separated at the other side thereof by a circumferential slit, the piston having a relieved area around each piston pinopening and a substantially U shaped slot located wholly within the relieved area below the ring grooves spaced from andsurrounding a portion of theopening to separate the piston pinboss from the skirt substantially entirely atopposite sides '1 of and below the piston pin opening, and unbalanced bearing strips extendinginto said relieved area from'opposite' side edges thereof and having their inner ends. spaced apart, said ends b'eing the ends of said U- shaped slot.

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